1. Field of the Invention
The present invention is related to the field of matting used in environmental applications to establish and reinforce vegetative channel and slope linings and trap and retain sediment in water flow. More particularly, to a high strength turf reinforcement mat (TRM) having a tightly woven or extruded corrugated body structure that, without fiber infill, effectively filters, traps and retains sediment carried in a water flow, the sediment acting as ballast to create greater contact between the TRM and the underlying substrate. The mat may also be used as a reusable sediment filtration mat to trap and retain sediment in runoff water flowing from construction sites to prevent sediment deposition into nearby water bodies. The use of the mat in both of these applications may be in conjunction with soil flocculating chemicals such as polyacrylamides and chitosans which enhance aggregation of soil particles and expedite settling of soil particles out of water flow.
2. Description of the Related Art
Turf reinforcement mats (TRM's) are typically used with seeded vegetation and for permanent reinforcement of mature vegetation. Without reinforcement, vegetation relies primarily upon the root system of each plant to bond to the channel or slope surface. Grass lined channels and slopes possessing root systems reinforced with synthetic mats are capable of withstanding more than two times the flow velocities and double the flow durations of grass linings that are not reinforced.
One weakness of TRM's is the ineffectiveness of such products if the mats are not held in continuous intimate contact with the underlying soil surface. Gaps and spaces between the bottom of the TRM and the underlying soil collect water and are prone to erosion. Such gaps also inhibit vegetation propagation through the TRM, which negatively impacts the TRM's primary goal of establishing and reinforcing vegetative linings. To ensure continuous intimate contact with the underlying soil, TRM's are often installed with a large number of anchors, such as sod staples, stakes or percussion earth anchors, per unit area of mat. To facilitate the necessary contact, many TRMs are manually soil-infilled during installation, which is a time-consuming and labor intensive process.
U.S. Pat. No. 5,849,645 (“the '645 patent”) discloses a reinforced composite matting for installation on a channel surface. The matting includes corrugated chambers formed by a very open netting structure. The chambers are in-filled with a fiber matrix that catches sediment from runoff passing through the channel which encourages seed germination and the establishment of root systems. While the fiber matrix can create a sediment entrapment effect, the fibers infilling the chambers actually take up space which could otherwise be available to accommodate more entrapped sediment. Further, the layers of composite matting in the '645 patent are stitched together with thread, limiting the overall strength of the mat and its resistance to layer separation when under high stress conditions. In addition, the reinforced composite matting of the '645 patent is secured in the channel with a large number of staples to anchor the netting to the underlying soil. Installing these anchors is time-consuming, labor intensive, and often does not accomplish sufficient continuous contact of the TRM to the underlying soil.
U.S. Pat. Nos. 5,567,087 and 5,616,399 to Theisen describe a single-layered, three dimensional soil protection mat produced from heat shrinkable monofilaments into a waffle or honeycomb pattern, with opposing adjacent pyramidal protrusions on each side of the mat. This structure provides only small diamond-shaped pockets for sediment entrapment within the mat, is not multi-layered and does not have a planar bottom layer to provide for increased sediment containment volume. Neither of the Theisen patents claim that the mats disclosed therein efficiently filter, trap and retain sufficient sediment to provoke self-anchoring of the mat.
Accordingly, a need exists for a TRM that is simpler to install and that can effectively filter, trap and retain sediment (soil/fine aggregate) carried in water flow to act as ballast and result in greater TRM-to-substrate contact with less need for the use of anchors and/or manual soil-infilling.
Furthermore, sediment control systems that include soil flocculating chemicals, degradable mats, and water clarification swales are now being used to clarify sediment-laden runoff water from construction sites. Sediment-laden runoff is directed into a swale or channel lined with a degradable mat typically made from jute or coconut fibers. The soil flocculants are administered at the upper portion of the swale or channel, causing small soil particles suspended in the water flow to aggregate and settle out on the surface of the degradable mat lining downstream. As these degradable mats are made from natural fibers and have no sediment entrapment chambers, they are limited in strength, sediment capacity and can only be used one time. Once sediment builds up on the mat surface, they are removed from the swale and discarded. Therefore, a need exists for a long-lasting, re-usable high strength sediment filtration mat that can be placed on the bottom of such clarification swales to more efficiently capture aggregated soil particles, with greater capacity to hold more sediment and sufficient strength to be lifted from the swale, washed clean of sediment, and re-used as desired.